This invention relates generally to leg type mobile robots, and particularly to a foot portion structure of a leg type mobile robot.
Among various known techniques for a leg type mobile robot, a technique related particularly to the structure of a foot of the leg type mobile robot is known in the art, for example, as described in US 2004/0238240 A1. A foot of the leg type mobile robot described in US 2004/0238240 A1 connects with an end of the leg through an ankle joint, and is composed of a force sensor (e.g., six-axis floor reaction force detector) for detecting floor reaction force, a spring mechanism provided with an elastic member (rubber bushing) having an impact absorbing function, a foot sole frame, a foot sole plate and a sole, which are arranged sequentially from above. This leg type mobile robot may be configured to achieve a high accuracy of floor reaction force detection because its reaction force detector is provided near a ground contact area, and to achieve a reduction of impact given upon landing with the help of the spring mechanism.
In such a leg type mobile robot as described in US 2004/0238240 A1, the elastic member compresses in a direction perpendicular to the ground contact surface of the foot when it absorbs a shock. The elastic member typically made of rubber exhibits a relatively small stroke (displacement) of compression, which could possibly be insufficient for fully absorbing the shock caused by landing, particularly for removing a high-frequency component thereof during a landing period for which a foot is landed on the ground. Furthermore, the relatively small stroke (displacement) of compression of the elastic member provided in this leg type mobile robot would reduce the longevity of the elastic member, each time when the elastic member is compressed to produce a sufficient reaction force during a bracing period for which one foot is braced against the ground to lift the other foot. With this in view, the leg type mobile robot may include another member or mechanism for absorbing a shock caused by the movement of the foot (shock-absorbing device), other than the elastic member.
It is appreciated that the displacement (stroke) for absorbing a shock in the foot of the leg type mobile robot is greater during the bracing period than during the landing period. In other words, the reaction force in the direction perpendicular to the ground contact area of the foot is relatively greater for the bracing period in comparison with that for the landing period. It would thus be desirable to provide the foot with flexibility such that the reaction force during the landing period is relatively small while the reaction force during the gracing period is relatively great. In particular, with the trend toward high-speed locomotion of the leg type mobile robot, the leg type mobile robot moves at high speed as the case may be, in which case the reaction force acting on the foot would become greater and thus the increased locomotive stability would be in need.
The present invention has been made in an attempt to attend to the above-described need.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.